A few years back, passengers waited in long queues to get a ticket, but now they can buy them

• A. A few years back, passengers waited in long queues to get a ticket, but now they can buy them
• B. A few years back, passengers waited in long queues to get a ticket, but now they can buy one
• C. A few years back, passengers will have to wait in long queues to get a ticket, but now they can buy one
• D. Sometime before, passengers were to wait in long queues for their tickets, but now they can buy